1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head that discharges liquid by bubbling it. More particularly, the invention relates to a method for manufacturing a liquid discharge head provided with a movable member which is displaceable by pressure exerted at the time of bubbling.
Also, the present invention is applicable to a printer for recording on a recording medium, such as paper, thread, textile, cloths, leather, metal, plastic, glass, wood, ceramics, and some others, as well as to a copying machine, a facsimile equipment having communication systems, and a word processor having a printer unit, among some others. Further, the invention is applicable to a recording apparatus of industrial use, which is complexly combined with various processing apparatuses.
In this respect, the term xe2x80x9crecordingxe2x80x9d used for the invention hereof means not only the provision of characters, graphics, and other meaningful images, but also, that of patterns and other images which are not meaningful.
2. Related Background Art
For a recording apparatus, such as a printer, there has conventionally been known an ink jet recording method, the so-called bubble jet recording method, in which images are formed on a recording medium by adhesion of ink discharged from discharge ports by action based on the abrupt voluminal changes that follow a bubble created by the application of thermal energy or the like to liquid ink in flow paths. A recording apparatus that uses this bubble jet recording method is generally provided with discharge ports for discharging ink; liquid flow paths communicated with the discharge ports; and electrothermal converting devices arranged in the liquid flow paths as means for generating energy used for discharging ink as disclosed in the specification of U.S. Pat. No. 4,723,129 and others.
In accordance with a recording apparatus and recording method of the kind, it is possible to recording high quality images at a higher speed in a lesser amount of noises. At the same time, the head of this recording apparatus makes it possible to arrange discharge ports for discharging ink in high density with many advantages, such as to facilitate obtaining recorded images in high resolution or color images by use of a smaller apparatus. As a result, the bubble jet recording method has been widely utilized for many office equipment including a printer, a copying machine, and a facsimile equipment, and further, utilized for industrial systems, such as textile printing apparatus, in recent years.
Along with the wider utilization of the bubble jet technologies for products in many fields, various demands have been brought increasingly in recent years as given below.
In order to obtain images in higher quality, there has been proposed a liquid discharging method or the like that regulates driving conditions to attain good ink discharges at high ink discharge speed on the basis of stabilized bubble generation or there has been proposed a liquid discharge head the configuration of flow paths of which is improved to make it possible to perform recording at higher speed, as well as to effectuate refilling liquid into flow paths at higher speed after liquid has been discharged.
Besides, such heads as described above, there is an invention disclosed in the specification of Japanese Patent Application Laid-Open No. 6-31918 in which attention is given to the back wave (pressure directed toward the side opposite to the discharge port) generated along with the creation of a bubble (bubbles), which incurs energy loss at the time of discharges, and a head is structured so as to prevent the back waves from being generated. In accordance with the invention disclosed in the specification of this Laid-Open Application, the back wave can be suppressed momentarily and slightly. However, since nothing is taken into consideration at all as to the correlations between the growth of bubble and the triangle portion, nor there is any conception thereof, this invention contains problems as given below.
In other words, a heat generating element is positioned on the bottom of each recessed portion by the invention disclosed in the specification of this Laid-Open Application, thus making it impossible to provide the linearly communicative condition with each discharge port. As a result, the shape of each liquid droplet is not stabilized, and furthermore, owing to the growth of bubble which is allowed to begin with the circumference of each vertex of the triangle portion, the bubble grows up to the entire side opposite to one side of the plate-like portion of the triangle. As a result, the ordinary growth of bubble is completed in liquid as if there was no plate-like member present. Then, for the bubble that has grown, the existence of the plate-like member has no relational effect at all. On the contrary, with the entire body of the plate-like member being surrounded by bubble, the refilling to the heat generating element positioned on the bottom of the recessed portion creates disturbance in the liquid flow, which causes a micro-bubble to be retained inside the recessed portion, leading to disorder in effectuating the principle of discharges itself, which is based on the growth of bubble.
Meanwhile, as disclosed in the specification of European Patent (EP) Application Laid-Open No. 436,047, it has been proposed to provide a first valve which is arranged between the vicinity of discharge port and bubble generating portion to cut them off, and a second valve which is arranged between the bubble generating unit and ink supply portion to cut them off completely, and then, to open and close these valves alternately (FIG. 4 to FIG. 9, EP Laid-Open Application 436,047). However, it is required by this invention to divide three chambers by two, respectively, which results in the creation of large tail that ink trails when it follows a liquid droplet at the time of discharge. Then, the number of satellite dots becomes much more than that of those formed by the discharge effectuated by the ordinary method in which bubble grows, shrinks, and becomes extinct in that order (presumably, this is because the effect of meniscus retraction that follows bubble extinction cannot be used). Also, at the time of refilling, liquid is supplied to the bubble generating portion along with the extinction of bubble. However, as no liquid can be supplied to the vicinity of discharge port until the next bubbling takes place, not only discharging liquid droplets vary greatly, but also, the response frequency of discharges becomes extremely small. Therefore, this invention has not attained the practical level as yet.
In this respect, the applicant hereof has proposed many inventions that use a movable member (a plate member or the like formed in a cantilever fashion, which is provided with the free end from the pivot thereof on the discharge port side) capable of contributing to the discharge of liquid droplets effectively unlike the conventional art described above. In the specification of Japanese Patent Application Laid-Open No. 9-48127, an invention is disclosed wherein the upper limit of the displacement is regulated for a movable member in order to prevent even a slight disorder from being given to the behavior of the movable member. Also, in the specification of Japanese Patent Application Laid-Open No. 9-323420, an invention is disclosed wherein the refilling capability is enhanced by the advantageous utilization of a movable member by shifting the position of the common liquid chamber to the free end side of the movable member, that is, on the downstream side. For these inventions, there is adapted a mode as a prerequisite in which the growing bubble is encircled by the movable member temporarily, and then, it is released from this stage to the discharge port side all at once. As a result, no attention is given to each individual element of the bubble related to the formation of liquid droplet itself as a whole nor any attention is given to the correlations between them.
In the next stage in this respect, the applicant hereof has disclosed an invention in the specification of Japanese Patent Application Laid-Open No. 10-24588 wherein a part of bubble generating area is released from a movable member with attention given to the bubble growth which is made by the propagation of pressure waves (acoustic waves) as element related to liquid discharge. Nevertheless, in this invention, too, no attention is given to each individual element of the bubble related to the formation of liquid droplet itself as a whole nor any attention is given to the correlations between them.
Conventionally, although it has been known that the front portion of a bubble created by film boiling exerts a great influence on discharge for the liquid discharge head of edge shooter type (that is, the type having the discharge ports on the front part of flow paths, which do not change liquid flow direction), there has been no invention any attention of which is given to enabling the front portion of the bubble to contribute more effectively to the formation of discharge liquid droplet. Now, therefore, the inventors hereof have ardently studies with a view to solving technical problems related thereto, and given attention further to the displacement of movable member and created bubble. As a result, the inventors hereof have acquired the effective knowledge as given below.
In other words, with the mode of flow path side walls taken into consideration, it is arranged to regulate the displacement of movable member by use of the flow path side walls along with the growth of bubble, and then, a structure is designed in order to regulate the movable member, and at the same time, to regulate the growth of bubble. More specifically, it has been found that with the provision of a stopper for the flow path side walls to be used for the movable member, the mode of growing bubble is regulated, while allowing the required liquid to flow, and that the tolerance range can be made wider for the micro- processing thereof.
In general, the larger the clearance between the movable member that is displaced in the flow path, and the flow path side walls which are positioned on the sides of the movable member, the better for absorbing the variation that may be caused to exist due to manufacture when arranging movable member. However, if this clearance is large, a problem is encountered that bubble enters the gap between the movable member and the flow path side walls positioned on the sides of the movable member by the growth of the bubble, and it grows around the movable member and has grown up to the upper surface thereof. As a result, there is no alternative but this clearance should be made as small as possible eventually. However, with the provision of stopper function for the flow path side walls that are positioned on the sides of movable member with respect to it, the aforesaid incompatible requirements can be met satisfactorily. In other words, even for a structure where the clearance is made large (5 xcexcm to 8 xcexcm, for example) to absorb the variation that may be caused due to manufacture when arranging liquid flow paths and movable members, the gap between the movable member and the stopper becomes narrower gradually as the movable member is displaced along with the growth of bubble, and then, the passage of bubble begins to be restricted when the gap becomes approximately 3 xcexcm. In this way, the passage of bubble is completely blocked on a part of the portion and the circumference thereof where the movable member and the stopper positioned on sides thereof are in contact with each other. In other words, bubble is not allowed to grow around to the upper surface of the movable member.
On the basis of such knowledge as described above, the side stopper is provided. In this case, with the bubble growth from the surface where bubble is created to the upper limit being regulated exactly, the bubble growth in the direction opposite to the discharge port is increased in the space between the movable member and the surface where the bubble is created. This type of bubble growth is not the element that may reduce the discharge efficiency. Therefore, it may be negligible. The inventors hereof, however, have made further studies for the rational utilization thereof for the displacement of movable member. As a result, a knowledge has been acquired to make it possible to utilize the growth of bubble rationally for the displacement of movable member by allowing the movable member to approach the bubble creation surface closely (20 xcexcm or less, for example), at the same time, forming integrally with the movable member a portion to receive pressure waves which is away from the bubble creation surface. Also, it has been found that the movable member that extends from the fixed end to the free end generates its actual fulcrum between the free end and the fixed end when it moves. As a result of further studies, it has also been found that fluctuation can be corrected by regulating the spatial volumes that essentially follow the movement of movable member.
Now, therefore, it is an object of the present invention to provide a method for manufacturing a liquid discharge head capable of forming the minute gap between movable member and side stopper more easily in higher precision.
The method of the present invention for manufacturing a liquid discharge head, which is provided with a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths, each one end thereof being communicated with each of the discharge ports, having bubble generating area for generating a bubble in liquid; means for generating a bubble to generate energy for creating a bubble to be grown; a plurality of liquid supply ports, each being arranged for each of the plurality of liquid flow paths to be communicated with a common liquid supply chamber; and movable members, each having fixed portion and movable portion supported with gap with the liquid supply port on the liquid flow path side, comprises the steps of forming a first gap formation member on an element substrate having the means for generating a bubble; forming movable member on the first gap formation member and the fixing member on the element substrate; forming a second gap formation member for the formation of gap between the side walls of the liquid flow path and the liquid supply port on the upper surface and sides of the movable portion of the movable member; removing the first gap formation member, while leaving the second gap formation member intact in the state of being closely in contact with the movable member; forming wall material at least on the second gap formation member and circumference of the movable member; patterning the wall material to form the liquid flow path walls and the liquid supply ports altogether; and removing the second gap formation member. Further, this method for manufacturing a liquid discharge head may be provided with a step bonding the element substrate provided with the bubble generating means, the movable member, the liquid flow path walls, and the liquid supply ports, and the ceiling plate provided with the common liquid supply chamber.
Also, another characteristic of the present invention lies in a method for manufacturing a liquid discharge head provided with a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths, each one end thereof being communicated with each of the discharge ports, having bubble generating area for generating a bubble in liquid; means for generating a bubble to generate energy for creating the bubble to be grown; a plurality of liquid supply ports, each being arranged for each of the plurality of liquid flow paths to be communicated with a common liquid supply chamber; and movable members, each having fixed portion and movable portion supported with gap with the liquid supply port on the liquid flow path side, comprising the steps of forming a first gap formation layer on an element substrate having the means for generating a bubble for the formation of a first gap formation member, and performing patterning; forming the fixing portion of the movable member having the same height as that of the first gap formation member in the portion on the substrate not occupied by the first gap formation member; forming the movable member on the first gap formation member and the fixing member; forming a second gap formation member for the formation of gap between the side walls of the liquid flow path and the liquid supply port on the upper surface and sides of the movable portion of the movable member; removing the first gap formation member, while leaving the second gap formation member intact in the state of being closely in contact with the movable member; forming wall material at least on the second gap formation member and circumference of the movable member; patterning the wall material to form the liquid flow path walls and the liquid supply ports altogether; and removing the second gap formation member. Further, this method for manufacturing a liquid discharge head may be provided with a step bonding the element substrate provided with the bubble generating means, the movable member, the liquid flow path walls, and the liquid supply ports, and the ceiling plate provided with the common liquid supply chamber.
Also, it is preferable for the step of forming the second gap formation member to comprise the steps of forming a second gap formation layer for forming a second gap formation member to cover the movable member; forming a mask layer on the second gap formation layer to form the second gap formation member; etching the second gap formation layer with dry etching process using the mask layer; and forming the second gap formation member by etching the second gap formation layer with wet etching process subsequent to the dry etching process. With the dry etching and wet etching thus executed dividedly in two stages, it becomes possible to form the second gap formation member more easily in higher precision. Further, it is preferable for the step of removing the first gap formation member to be a step of removing altogether the first gap formation member, and the mask layer for forming the second gap formation member with wet etching process. Also, it is preferable for the step of forming the mask layer to be a step of forming a mask layer with one and the same material as the film used for the first gap formation member. In this way, it becomes possible to reduce the number of manufacturing steps and manufacture the liquid discharge head at lower costs.
The material of the first gap formation member is preferably aluminum, Al/Cu, Al/Si, or other aluminum alloy, and the material of the second gap formation member is preferably TiW, W/Si, W, or other tungsten alloy. The tungsten alloy has light shielding capability to be able to function as a mask usable at the time of exposure, and also, while it is resistive to etching solution generally used for removing the Al film pattern or resin that serves as a sacrifice layer or the like, it has an advantage that the etching process becomes selective, because it can be removed by use of a designated etching solution (hydrogen peroxide).
It is preferable for the step of patterning wall material to form the liquid flow path walls and the liquid supply ports by photolithographic process using negative type resist. Further, for the step of patterning wall material, it is preferable that the mask pattern. which is used in the exposure step for the liquid flow path walls and the liquid supply ports, should be provided with a wider projection area of non- photosensitive portion than the projection area of the second gap formation member on the movable member.
With the method thus structured, it becomes easier to form the side stopper that supports the movable member stably in a state where the displacement of the movable member is regulated to close the liquid supply port, and also, it becomes possible to form the minute gap between the movable member and the side stopper more easily in higher precision.
Furthermore, the liquid discharge head, which is manufactured in accordance with the present invention, makes it possible to cut off immediately the communicative condition between the liquid flow path and the liquid supply port by means of movable member within a period during which bubble is being grown almost isotropically at the earlier stage of bubble creation by means for generating a bubble, and then, with the structure which is arranged so that the interior of the liquid flow path is essentially closed with the exception of the discharge port, the pressure waves generated by growing bubble in the bubble generating area is not allowed to be propagated to the liquid supply port side or to the common liquid supply chamber side. Most of the pressure waves are directed toward the discharge port side, thus enhancing the discharge power significantly. Also, even when a highly viscose recording liquid is used for a high-speed fixation on a recording paper sheet or the like or used for eliminating spread on the boundaries between black and colors, it becomes possible to discharge such highly viscose ink in good condition with the significantly enhanced discharge power. Also, due to environmental changes at the time of recording, particularly under the environment of low temperature and low humidity, the discharge port tends to have more area where the viscosity of ink increases, and ink is not allowed to be discharged normally in some cases at the time of use initiation. However, even under such circumstances, the present invention makes it possible to perform discharging in good condition from the very first shot. Also, with the significantly enhanced discharge power, it becomes possible to reduce the size of heat generating element serving as means for generating a bubble or to reduce energy to be inputted for discharging accordingly.
Also, with no pressure waves of the bubble growth in the bubble generating area being allowed to be propagated to the liquid supply port and the common liquid supply chamber side, there is almost no shifting of liquid to the common liquid supply chamber side, hence minimizing the retracting amount of meniscus at the discharge port after liquid droplet has been discharged. As a result, it is quick to complete ink replenishment (refilling) to the liquid flow path in a designated amount, thus enhancing the discharge frequency significantly when highly precise ink discharges (determinate quantity) are performed.
Also, in the bubble generating area, bubble grows largely on the discharge port side, while suppressing the growth thereof toward the liquid supply port side. As a result, the point of bubble extinction is positioned in the portion on the discharge port side from the central portion of the bubble generating area. Then, the power of extinction thereof can be reduced, while maintaining the bubbling power. This contributes greatly to the enhancement of mechanical and physical breaking life of heat generating element due to the power exerted by bubble extinction in the bubble generating area.